It has been found that introduction of urea into the exhaust gasses streaming from an combustion engine and into a catalytic system may dramatically increase the efficiency of the catalytic element's capability to convert NOx gasses. While urea in it self is relatively harmless to the environment and the amounts introduced into the combustion system thereby can be overdosed, such wasting of urea is often undesirably as the technology is often applied to moving vehicles and such waste would require larger storage capacities than what is actually needed if urea is dosed correctly.
A need for introducing the required amount of urea into the exhaust gasses only is therefore present. Furthermore, urea is most efficiently introduced into the exhaust gasses as a spray of droplet which typically requires that the urea is pressurized and fed to a nozzle.